First experimental observation of the ignition of a ‘‘superdense glow’’ before the glow-to-arc transition in a pseudospark discharge

Abstract

The presented results are the first experimental indication for the existence of a homogeneous superdense glow in the bore hole of the cathode in a pseudospark discharge. The start of this mechanism is leading to the low-impedance high-current phase and starts before the glow-to-arc transition in the pseudospark discharge. It is assumed that the high-current density is carried mainly by metal ions which originate from a self-sustained self-sputtering mechanism, or by a large number of, on a macroscopic scale, homogeneously distributed Schottky emitters. It is shown that the geometric features of the bore hole cause an enhancement of this effect. These results and the theoretical assumptions can also explain very effectively the current quenching of the pseudospark discharge. Current quenching is only occurring during the superdense glow when no cathode spots are ignited.

Investigation of the high current stages in pseudospark discharge

“…It is known that the dense phase of a glow discharge can not exist long enough [4,5]. The discharge begins to localize in the hole in the cathode, while on the surface of the cathode begin to observe the numerous micro spots, burning voltage drops decreases and current increases and the discharge goes into a stage of superdense glow discharge.…”

“…i a = i c = S p en e V e /4 exp(−eΔV/kT e ) , (4) where S p is area of the plasma column near the anode, v e = (8kT e /m) 1/2 -the average velocity of the electrons.…”

“…At present, the discharge is widely used in the development of high current switching, generation of extreme ultraviolet radiation and so on [1][2][3]. It is known that the discharge during of its development goes through several stages, each characterized by its localization in the plasma electrode system and apparently by current transport mechanism [4][5][6]. However, if the physical processes in the prebreakdown, low-current stage adequately studied [7,8], while the study of high current stages of dense and superdense glow discharges a number of issues appear.…”

Low-pressure discharges with hollow cathode and hollow anode and their applications

“…Reprinted from [12], with the permission of AIP Publishing. Stage III is the so-called superdense glow discharge [2,41,[80][81][82][83]. The new drop in voltage accompanies the transition to this stage.…”